The present invention relates to the arrangement of recorded data on an information recording medium. More particularly, it relates to an information recording medium including information arranged thereon so as to allow restricted writing and reading in a commonly current write and read drive, and a system for performing restricted write and read operations on and from the information recording medium.
One example of a conventional optical recording system will be described with reference to FIGS. 3 and 5 as one example of an information recording system.
FIG. 3 shows a block diagram of a conventional optical write and read drive. The light beams emitted from a laser 25 (with a wavelength of about 660 nm for a DVD-RAM), which is a part of a head 2, are collimated into a nearly parallel light beam 22 through a collimating lens 24. The light beam 22 is applied onto an optical disk 11 through an objective lens 23 so as to form a spot 21. Thereafter, the reflected light beams are guided through a beam splitter 28, a hologram element 29, or the like, to a servo detector 26 or a signal detector 27. A signal from each detector is subjected to an add/subtraction process to become a servo signal, such as a tracking error signal or a focus error signal, which is then inputted to a servo circuit. The servo circuit controls the positions of a driving means 31 of the objective lens 23 and the whole optical head 2 based on the tracking error signal and focus error signal that has been obtained, so that the optical spot 21 is positioned in an objective writing and reading area. An added signal from the detector 27 is inputted to a signal reproduction block 41. In a signal processing circuit, the inputted signal is subjected to a filtering process and a frequency equalizing process, and then is subjected to a digitization process. The digital signal thus subjected to a digitization process is processed by an address detector and a demodulation circuit. Based on the address signal detected by the address detector, a microprocessor calculates the position of the optical spot 21 on the optical disk 11 and controls a position control means, thereby to position the optical head 2 and the optical spot 21 at an objective recording unit area (sector).
If the instruction from a host to the optical write and read drive is a writing instruction, the microprocessor receives recording data from the host and stores it in a memory, while controlling the position control means to position the optical spot 21 at a position in an objective recording area. The microprocessor checks that the optical spot 21 has been properly positioned in the recording area by an address signal from the signal reproduction block 41, and then controls a laser driver and the like to write the data in the memory on an objective recording area.
An address signal is arranged in every information recording unit area, at the beginning portion of the recording unit area, as shown in FIG. 6. Therefore, it is possible to check the position of the optical spot immediately before writing by detection of the address signal.
FIG. 5 shows an example of the flow of operation of an optical recording system for driving the DVD-RAM disk specified in International Standard ISO/IEC-16824, or the like, which is a rewritable DVD or DVD-RAM representing one example of the optical recording system described above.
When a disk is loaded, or the power of the optical recording system is turned on, first, the optical recording system performs a process for discriminating the types of media. In general, it has a function of reading a CD-ROM or DVD-ROM which is a read-only medium, in addition to the DVD-RAM medium. Therefore, the optical recording system first performs a media type discrimination process to discriminate which one of the types described above the medium corresponds to. Individual systems perform the discrimination process in mutually different ways. For example, some systems discriminate the types of media from the analogue characteristics of the reflectance and the reproduced signal, such as the focus error signal, and other systems read a physical information area provided on a disk substrate and then discriminate the types of media based on the contents (data).
If the optical recording system identifies the type of the medium as a rewritable type, i.e., a DVD-RAM, first, it checks the recorded contents of a defect management information area, and the like, and thereby checks whether the optical disk has been physically formatted. If the optical disk has not been physically formatted, a wait period is initiated until a physical format command is issued from a host or a user.
If the optical disk has been physically formatted, the optical recording system performs a process of preparation for writing, such as a calibration process or logical consistency verification, and then it enters a wait state for a command from a user or host. Upon receiving some command, the optical recording system checks the type of the command. Then, if it is a write command, the optical recording system performs a writing process. For commands of read, format, unloading of the disk, and the like; the optical recording system performs respective corresponding processes. In general, these processes are normally terminated. However, in case of an unsuccessful write operation for an unexpected reason, the system performs an error handling process, such as retry or replacement.
In general, with a DVD-RAM, during the writing process, whether the recording data has been normally written or not is checked by actually reading the recorded data. If required, replacement is performed by using another recording unit area, thereby to enhance the reliability of the recorded data. The management information on the reallocation of recording areas due to the replacement is written in a specific area (defect management area).
Thus, the DVD-RAM is an optical recording system having very high reliability. However, since the recorded data is basically freely rewritable, it is not possible to eliminate the possibility that the important data already recorded is erased or rewritten due to a wrong operation by a user, a malfunction of the host, or the like.
Further, replacement is performed on the following precondition: even if rewriting processes are performed for a sufficiently larger number of times than the number of defects storable in the defect management area, it is possible to perform writing and reading with no problem.
As one method of protection, there is a so-called write protection function. However, the write protection can be freely revoked by a user. Accordingly, it is still impossible to prevent data corruption by the wrong operation of a user.
An example of a magneto-optical disk will be described as a proposal for overcoming such a problem. The magneto-optical disk is a rewritable storage medium that is capable of erasing and rewriting user data with respect to a user data area including user data recorded therein. However, there is a demand for this to be used as a WORM type storage medium not capable of erasing and rewriting user data.
For example, with a CCW method specified in International Standard ISO-1EC11560 (or a MO-WORM method), media type identification data indicative of the type of the magneto-optical disk is included in a control information area provided in an area outside the user data area of the magneto-optic disk. As a result, it is possible to identify whether the magneto-optical disk is of a rewritable type or a WORM type based on the media type information.
The magneto-optical disk drive is so configured that, if the WORM type magneto-optical disk is loaded therein, the erasing operation and the rewriting operation are not to be performed with respect to the user data area including user data already written therein. Namely, the magneto-optical disk, which is originally of a rewritable type, is provided with a write protection function for preventing erasing and overwriting. Consequently, it becomes possible to access a WORM type magneto-optical disk having a write protection function and a rewritable magneto-optical disk with the same magneto-optical disk drive. Accordingly, the magneto-optical disk drive finds a wider range of application, and it is also possible to reduce the media cost.
However, if an attempt is made to apply the same method to an optical disk system with only a rewritable type standard already set therein, such as a DVD-RAM, the following problem occurs.
The standard of the rewritable disk already exists, and such a disk is commercially available. An optical disk system for driving an optical disk in conformity with the standard also already exists. Even if media type data of the media type identification data area is newly defined, as in the example of the magneto-optical disk under such circumstances, it is not possible to change the existing drive. Therefore, it is impossible to control the operation of the existing optical disk drive having no write protection function.
Actually, as described above, all optical recording systems do not utilize media type identification data for discriminating the media types. Further, even if novel encoded data which has been undefined in the art is written to the media type identification data, the operation has been undefined because a conventional optical recording system cannot recognize the meaning of the encoded data.
Namely, in the prior-art example, there has been a risk that the data on the optical recording medium is corrupted by a mistake with the existing recording drive when a medium with a restriction on its function, such as a low-priced medium providing low overwrite cyclability is introduced.
It is an object of the present invention to provide a secure optical recording system which imposes a restriction on its method of use, for example, imposes a substantial restriction on the rewrite count of a medium without changing the hardware or physical specifications, and eliminates a risk that recorded information is corrupted or recorded information is lost as with a conventional drive even for a medium with low overwrite cyclability or a low-priced medium.
The following features were Used in order to attain the object of the present invention.
(1) Out of user recording blocks of the information recording medium, at least one or more blocks have been set to be unrecordable, unreadable, or inaccessible restricted blocks. The term xe2x80x9crestrictedxe2x80x9d as herein used denotes that a restriction is imposed on the rewrite count of a specific area, such as a defect management area.
Consequently, it is possible to disable the substantial use thereof in a system which does not recognize the presence of the restricted block. Accordingly, it becomes possible to force the use of specific control software or a specific logical format, thereby making it possible to restrict the method of use of the disk. For example, it becomes possible to prohibit the use of a disk shipped with a specific logical format by reformatting the disk in another format, or the like. By utilizing this fact, it becomes possible to use a medium with a restriction on its overwrite cyclability with security, as will be described later.
(2) The user recording block has been set to be an error correction code (ECC) block composed of a plurality of user sectors. Consequently, it becomes easy to apply the present invention to a system which records data in a unit of the ECC blocks (such as a DVD-RAM). The ECC block, which is the unit for recording, is not necessarily required to be in agreement with a sector, which is the minimum unit of the addressable block as seen from the host system. For example, in a DVD system, 2048-byte user data can be stored in one sector, and the ECC block is composed of 16 sectors, i.e., data of about 32 kB.
(3) The user sectors individually have independent address numbers, and all the user recording blocks to which the user sectors belong, which have the smallest 257, or more desirably 513, address numbers out of the user sectors, have been set to be at least unrecordable, unreadable, or inaccessible restricted blocks. Alternatively, all the user recording blocks to which the user sectors belong, which have the largest 257 address numbers out of the user sectors, have been set to be at least unrecordable, unreadable, or inaccessible restricted blocks. Namely, the lowermost 257 blocks or 513 blocks, and/or the uppermost 257 blocks, in the user address space have been at least substantially set to be disabled.
Consequently, it is possible to substantially make it impossible to format or reformat a recording medium for use by ordinary logical formatting software whereby a file system area is arranged at the beginning portion of the user area. Therefore, it is possible to substantially restrict the use of the format using other formatting software than the objective software of the present invention. Thus, it is possible to restrict the method of disk use with reliability. Particularly, it is possible to restrict the ordinary formatting with reliability in a UDF file system using sectors 256 and 512 as reference sectors (AVDPs: Anchor Volume Descriptor Pointers). Since some file systems allocates system information to the end portion of the volume space (data area), it is more desirable for the disabled area to be also allocated to the end portion.
(4) An information recording medium is used, which comprises: at least a plurality of independently writable and readable user recording blocks; and spare blocks each for replacing a user recording block having a defect, wherein at least one or more blocks out of the spare blocks have been set to be an unrecordable, unreadable, or inaccessible restricted blocks.
Consequently, it becomes possible to apply the write restriction method even to a system having a replacement function (ex., DVD-RAM) with reliability.
For achieving the foregoing object, it is desirable to use an information recording medium, which comprises: at least a plurality of independently writable and readable user recording blocks, and three or more blocks of spare blocks, each for replacing a user recording block having a defect, wherein at least three or more consecutive blocks out of the spare blocks are unrecordable, unreadable, or inaccessible restricted blocks. In a conventional DVD-RAM system, when a defect exists in the block itself to be used as a spare block, its adjacent recording blocks are automatically reallocated as spare blocks. However, if three or more consecutive blocks are disabled, as described above, it becomes impossible to normally perform the reallocation function. Consequently, it is possible to impose a restriction on the use with higher reliability.
(5) As a means for implementing the unrecordable, unreadable, or inaccessible restricted blocks a medium is used in which address numbers are arranged as the physical address data, each made up of at least a code indicative of an address number and an address error detection code for verifying the correctness of the address number, and some of the address numbers are at least included, in each of which there is a mismatch between the codeword indicative of an address number and the error detection code for verifying the correctness of the address number. Consequently, with a conventional drive, address detection is disabled, so that the corresponding portion becomes unrecordable, unreadable, or inaccessible. Since some systems ignore a little address error, it is recommendable that a plurality of, and more desirably three or more blocks, each with address mismatch, are included in the blocks in order to impose a restriction on writing with higher reliability.
(6) The address number is arranged as the physical address data made up of at least a code indicative of an address number and an address error detection code for verifying the correctness of the address number on the recording medium. As for the physical address data corresponding to the unrecordable, unreadable, or inaccessible restricted blocks out of the physical address data, each address number indicated by the physical address data has been set to be different from the address number of the block. Consequently, it becomes impossible to gain the objective address with a conventional drive, so that the corresponding portion becomes unrecordable, unreadable, or inaccessible.
(7) An information recording medium is used which comprises at least two or more independently writable and readable user recording blocks, wherein out of the user recording blocks, at least one or more blocks are unrecordable, unreadable, or inaccessible restricted blocks. Further, a map or list of information indicative of the existing positions or addresses of all the restricted blocks are prerecorded as encoded data or encrypted data on a specific area or desirably on a read-only area where information is recorded by embossed pits or the like on the information recording medium.
Consequently, only a processing system capable of decoding the specific authorized cipher can use the recording medium of the present invention. Therefore, it becomes possible to ensure security.
(8) The recording medium is to be previously logically formatted so that an area, except for that of the unrecordable, unreadable, or inaccessible restricted blocks, is a substantial user area prior to shipment.
Consequently, it becomes possible to perform writing and reading on the medium of the present invention without any specific software in a conventional system. Even in such a case, the medium substantially becomes unusable if it is formatted in another system, and hence it is possible to substantially restrict the method of use so as to be different from the intended method of use of an information recording medium provider. Therefore, it becomes possible that the recording medium manufacturer assumes the restricted use method of the medium. Consequently, the flexibility of the specifications is increased, so that it becomes possible to provide a substantially low-priced recording medium.
(9) The write restriction as described above has been implemented by configuring a system such that an information recording medium having a write and read restriction comprising at least two or more independently writable and readable user recording blocks, out of the user recording blocks, at least one or more blocks being unrecordable, unreadable, or inaccessible restricted blocks, is used in a computer system or a write and read drive having a processing function for performing read and write control, such that an area except for the restricted blocks, is a substantial user area.
This system is so configured that, for example, a standard read and write drive is connected to a host onto which specific control software has been installed.
(10) An information recording and reproducing system having a write and read restriction has been configured which comprises: an information recording medium having a write and read restriction comprising at least two or more independently writable and readable user recording blocks, out of the user recording blocks, at least one or more blocks being unrecordable, unreadable, or inaccessible restricted blocks; and a means having a processing function for reading encoded data or encrypted data stored in a specific area on the recording medium, and decoding or decrypting the read data to obtain layout information of the restricted blocks, and performing at least one of write and read control or logical format, such that all the restricted blocks are not substantially user areas based on the restricted block layout information obtained by using the information recording medium.
Consequently, it becomes easy to add high security to the specification restriction. Accordingly, it becomes easy to restrict the use by an unauthorized user, or to restrict the use of software.
(11) An information recording and reproducing system has been configured whereby the restricted blocks are substantially excluded from the user area by registering the restricted blocks as defects, or the restricted blocks are substantially excluded from the user area by registering the restricted blocks as invisible files.
This enables the use of a restricted disk.
(12) An information recording medium is used which comprises: at least a plurality of independently writable and readable user recording blocks; and spare blocks each for replacing a user recording block having a defect, wherein the number of the spare blocks has been set to be smaller than the overwrite cyclability of the recording medium.
For example, in a 120-mm-dia DVD-RAM (4.7 GB per side), a PSA (primary spare area) and an SSA (supplementary spare area) can be ensured as spare blocks. Out of these areas, only the PSA is assigned at the time of shipment, and further, a part of the area is previously registered as used blocks. Consequently, the number of newly usable spare blocks is set to be smaller than the overwrite cyclability determined by the physical characteristics of the recording layer of the medium.
As a result, the write and read drive performs replacement registration when a defect is newly found during use of the medium, and every time the replacement registration process is performed, the defect management area, which is a specific area of the medium, is rewritten once. By using this technique, it is possible to restrict the number of cycles for rewriting the defect management area associated with the replacement to not more than the number of usable spare blocks, i.e., the rewrite count of the medium. This eliminates the danger that the rewrite count of the defect management area exceeds the overwrite cyclability. Consequently, the reliability of the medium is improved.
(13) An information recording medium is used, which comprises: at least a plurality of independently writable and readable user recording blocks; spare blocks each for replacing a user recording block having a defect; and at least a defect management table recording area for recording the relationship between the defective blocks and the spare blocks, wherein a plurality of the defective blocks and the spare blocks have been previously recorded in the defect management table, and the number of residual blocks registrable in the defect management table has been set to be smaller than the overwrite cyclability of the recording medium.
For example, in a 120-mm-dia DVD-RAM (4.7 GB per side), the defect management tables are of two types: a PDL (primary defect list) table and a SDL (secondary defect list) table. Out of these, in the PDL table, about 7000 sectors of defects can be registered, and about 4000 blocks of defects can be registered in the SDL table. In this way, most of the entries of the SDL table are assigned by replacement registration. Further, a part of them are previously registered as having been used to be the used blocks. Consequently, the number of defective blocks usable by additional assignment is set to be smaller than the overwrite cyclability determined by the physical characteristics of the recording layer of the medium.
As a result, the write and read drive performs defect registration when a defect is newly found during use of the medium, and every time the replacement registration process is performed, the defect management area, which is a specific area of the medium, is rewritten once. By using this technique, it is possible to restrict the number of cycles for rewriting the defect management area associated with the defect management to not more than the number of usable spare blocks, i.e., the overwrite cyclability of the recording medium. This eliminates the danger that the rewrite count of the defect management area exceeds the overwrite cyclability. Consequently, the reliability of the medium is improved. Herein, the defect registration denotes that a defect is registered as a defect, and it is not necessarily identical with the replacement assignment.
Any of the replacement assignment in the foregoing section (12) and the defect registration in the foregoing section (13) results in rewriting of the defect management area. Therefore, it is desirable that the sum of both the number of the spare blocks and the number of residual blocks registrable as defects is set to be smaller than the overwrite cyclability of the recording medium.
Further, at worst, there can be present the case where the replacement assignment described in the foregoing section (12) is performed after the defect assignment described in the foregoing section (13), and then, after spending the spare blocks, defect registration is performed with no replacement as in the means (13). Any of the steps results in rewriting of the defect management area. Therefore, it is more desirable that the number of the spare blocks and the number of the residual blocks registrable as defects are set to be smaller than one third of the overwrite cyclability of the recording medium, respectively.
(14) The total number of the restricted blocks on the information recording medium has been set to be larger than the total number of the recording blocks registrable in the defect management table. Consequently, even if an attempt is made to perform reformatting with certification, all the uxcx9cxrecordable blocks (restricted blocks) cannot be registered as defects. Accordingly, reformatting is unsuccessfully terminated. Namely, it is possible to disable (restrict) reformatting.
Other and further objects, features and advantages of the invention will appear more fully from the following description.